Business forms in cut sheet format having at least one label (with pressure sensitive adhesive) and suitable for variable printing in a non-impact printer (such as a laser printer or other printer using a heat-curable toner) are referred to as integrated labels, and are exemplified by U.S. Pat. No. 5,129,682. In current manufacturing processes a hot melt extrusion die adhesive application method is utilized in which a continuous stream of pressure sensitive hot melt adhesive is applied to a release web, the release web is laminated to a paper web, one or more labels are die cut, and a continuous form format is cut into individual sheets. The paper face sheet typically comprises 20-28 lb. per 500 sheets of paper per ream with dimensions of 17.times.22 inches! bond paper, while the release sheet is typically 25-50 lb. per 500 sheets of paper per ream with dimensions of 22.times.36 inches! weight material. While this technique is extremely efficient and cost effective, the integrated label produced has pressure sensitive adhesive extending to at least one, and typically to two opposite cut edges of each form. This presents a significant contamination problem in non-impact printers for variably printing indicia on the integrated labels, such as laser printers or other non-impact printers utilizing a heat curable toner to apply indicia. Contamination can occur in the nip rolls for the laser printer, or in other printer paper guiding and feed system components, and the build up of adhesive can eventually cause poor performance of the printer or terminate its operation altogether, the adhesive building up due to the tacky nature thereof.
One way in which the above mentioned problem can be avoided is to apply the adhesive in a pattern rather than in a continuous strip. When applied in a pattern, the pattern includes a hiatus at the edges where the continuous web will be cut into sheets. However this manufacturing method is slower and more costly than the extrusion die continuous strip method. Therefore it is desirable to be able to solve the problem of the adhesive contaminating laser printers which act upon the integrated labels while at the same time allowing manufacture using the continuous strip application of pressure sensitive adhesive.
According to the present invention the desired results of preventing printer contamination as a result of adhesive built up, while still allowing production of the integrated labels utilizing the continuous strip method, are provided. The invention accomplishes these desired goals by utilizing as the pressure sensitive adhesive an adhesive that becomes de-tackified by direct exposure to a sufficient type and dosage of electromagnetic radiation. Typically this is accomplished utilizing a specially formulated hot melt adhesive that is sensitive to ultraviolet energy so that when exposed to, e.g., about 3000 mj/cm.sup.2 total dosage of ultraviolet radiation, the edges of the integrated labels (where the release and bond sheet overlap) is rendered de-tackified, and therefore will not interfere with operation of, or otherwise contaminate, a non-impact printer. There are several aspects of the present invention employing this basic concept.
According to one aspect of the present invention a method of producing a sheet having at least one label and suitable for variable printing in a nonimpact printer, is provided. The method comprises the steps of: (a) Applying a continuous strip of pressure sensitive adhesive, that is de-tackified by direct exposure to a sufficient type and dosage of electromagnetic radiation, to a release sheet. (b) Applying the release sheet to a first face of a web of paper so that the release sheet covers only a portion of the first face and the adhesive is attached to the web. (c) Forming at least one label in each of a plurality of predetermined lengths of the web at the portion of each web predetermined length covered by the release sheet. (d) Cutting the web into individual sheet lengths, each sheet having at least a first edge of the paper at which the release sheet is provided. (e) Exposing the first edge to the sufficient type and dosage of the electromagnetic radiation that de-tackifies the adhesive so that the adhesive at the first edge becomes de-tackified. And, (f) subsequently using the sheet in a heat-curable toner non-impact printer.
The adhesive is preferably rendered de-tackified by ultraviolet radiation, and step (e) is practiced by exposing a sheet to ultraviolet radiation, e.g. exposing hot melt adhesive to about 3000 mj/cm.sup.2 total dosage of ultraviolet radiation.
The first edge may be a common edge of the paper and release sheet, and there may be the further step (g), between steps (d) and (e) of stacking a plurality of sheets in a stack with substantially aligned first edges. Step (e) is then practiced with the sheets in the stack (although alternatively step (e) may be practiced on individual sheets). Step (g) may be further practiced by placing chip board material on the top and the bottom of the stack.
Steps (a) through (d) may be practiced so that opposite first and second edges are commonly formed by the paper and release sheet, and step (e) may be practiced to apply electromagnetic radiation to the first and second edges one immediately after the other. Steps (a) through (d) may also be practiced so that a third edge, perpendicular to and extending between the first and second edges, is also commonly formed by the paper and release sheet, in which case there is the further step--either before or after step (e)--of exposing the third edge to a sufficient type and dosage of the electromagnetic radiation that the adhesive at the third edge becomes de-tackified.
There may also be the further steps, prior to step (f) of stacking a plurality of sheets in a stack, wrapping the stack in packaging, transporting the packaging to the site of the non-impact printer, and unpackaging the stack at the site of the non-impact printer.
According to another aspect of the present invention there is provided a method of acting upon a sheet comprising a first ply of paper and a second ply of a pressure sensitive adhesive release material overlapped with the first ply, with a pressure sensitive adhesive in a continuous strip between the first and second plies and holding them together in overlapped position, the second ply adjacent the first ply at at least a first edge of the first ply, the pressure sensitive adhesive being capable of being rendered de-tackified when directly exposed to a sufficient type and dosage of electromagnetic radiation, and at least one label formed by the first ply where the first and second plies overlap, the method comprising the step of (a) applying to the first edge the type of electromagnetic radiation with sufficient intensity and duration so that it de-tackifies the adhesive, so that the adhesive at the first edge becomes de-tackified. The detailed operations and steps, as described above, may also be utilized in the practice of this aspect of the invention.
The invention also comprises an integrated label. The integrated label of the invention has the following components: A first paper ply having a quadrate configuration and four edges and a first area. A second quadrate ply comprising a pressure sensitive adhesive release sheet having four edges. The first and second plies overlapping, including a first edge of the first ply aligned with or overlapped by the second ply. A continuous strip of pressure sensitive adhesive disposed between the overlapping portions of the first and second plies, releasably holding them together. At least one label formed in the first ply at the overlapping portions of the first and second plies. And, the adhesive at the first edge being de-tackified so that it will not stick to or interfere with continued operation of component parts of a heat-curable toner non-impact printer if the integrated label is passed through the printer, and the adhesive is tacky at the at least one label.
The second ply may have a second area significantly smaller than the first area, and the first edge of the first ply may be aligned with the first edge of the second ply and a second edge of the first ply aligned with a second edge of the second ply. In this case the adhesive at the second edge is also de-tackified so that it will not stick to component parts of or interfere with continued operation of a heat-curable toner non-impact printer if the integrated label is passed through the printer. The integrated label may be in a stack with a plurality of identical integrated labels having aligned edges, and the pressure sensitive adhesive may be a hot melt adhesive that becomes de-tackified when exposed to ultraviolet radiation.
According to another aspect of the invention there is provided apparatus for handling multi-ply sheets with pressure sensitive adhesive between the plies which is rendered de-tackified by direct exposure to ultraviolet radiation. The apparatus comprises: A stacker for stacking a plurality of sheets into a stack having aligned edges, and at least one ultraviolet radiation source emitting ultraviolet radiation that renders the adhesive de-tackified. A first conveyor may also be operatively associated with the stacker for conveying sheets in a first direction, and having first and second sides generally parallel to the first direction. The at least one ultraviolet radiation source preferably is adjacent to one of the first and second sides of the first conveyor for emitting ultraviolet radiation so that it is directed upon at least one edge of the sheets in the stack when the stack is on the first conveyor.
Each source of ultraviolet radiation may be a 300 nanometer nominal frequency, 300 watt/inch ultraviolet radiation source. The at least one source may comprise first and second sources mounted adjacent to the first and second sides of the first conveyor, respectively, and the first source may be mounted for movement toward and away from the second source to readily accommodate different size sheet edges between them. A third ultraviolet radiation source associated with a second conveyor extending perpendicular to the first conveyor also may be provided. Packaging means, a 90.degree. conveyor, a turn table, and like components may also be associated with the apparatus, and a stacker may be provided either upstream or downstream of the first conveyor in the first direction.
It is the primary object of the present invention to provide for the quick and inexpensive extrusion die continuous strip method production of integrated labels, which labels do not have active adhesive at the edge portions thereof so that they will not interfere with continued operation of non-impact printers. This and other objects of the invention will become clear from an inspection of the detailed description of the invention, and from the appended claims.